But what about if I want to have a mirrored copy also on Oracle ASM ?It's simply not possible even if from the documentation I didn't find about it./u01/app/11.2.0/grid/bin/crsctl add css votedisk +DATA_RAC3CRS-4671: This command is not supported for ASM diskgroups.CRS-4000: Command Add failed, or completed with errors.

The command is not supported. I can mention this documentation note from "Clusterware Administration and Deployment Guide" (e10717.pdf):Oracle does not support storing the OCR on different storage types simultaneously, such as storing OCR on both Oracle ASM and a shared file system, except during a migration.